Variable length reinforcement to control seat back performance

ABSTRACT

A modified seat frame provides a seat back frame mounting reinforcement which can be conveniently varied in length and strength to vary the allowed degree of deflection and energy absorption provided by the seat back upon rear impact.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to school bus seats and more particularly to a structural member used to reinforce seat joints and thereby control the location and degree of deformation of the seat back upon rear impact by an object.

2. Description of the Problem

School bus seats are built to meet many differing customer specifications. For example, some bus seats must accommodate three point safety belts by providing a compatible upper back rest, other specifications call for a universal child restraint attachment equipped lower frame, while still others provide standard DOT (United States Department of Transportation) seat backs. Alternatively, customers can specify seats in different widths or heights and can demand various strength requirements. School bus passenger seats vary in height and width resulting in different seat back performance characteristics. FMVSS (Federal Motor Vehicle Safety Standard) 222 requirements dictate the seat back deflection be controlled to fall within a specified window of force versus deflection. The specified window has minimum as well as maximum limits for this deflection.

Differing customers' specifications have required substantially or entirely different component sets. The need to supply such component sets has even occurred relative to completed vehicles that have been put into service where the vehicle has been moved from one state or municipality to another, based on differing requirements of the new jurisdiction. The variability in size has contributed to varying component sets meant to meet strength standards. Multiple tubes, brackets and gussets are incorporated into welded seat assembly. Components were added to the various seat assemblies until the resulting design was compliant. Various seat widths and heights may use different hardware based on these changes. Therefore, seats have exhibited additional variation in component parts to meet the FMVSS 222 requirements.

SUMMARY OF THE INVENTION

The invention provides for placing the variability relating to seat back strength and the degree of allowed deflection under force to be focused into one reinforcement component. In a modular seat frame the seat back has its foundation in an aisle riser and a wall riser, and includes a perimeter frame provided by a partial perimeter tube mounted at opposed ends in necks extending from the aisle riser and wall riser. A reinforcement member fits into the neck/partial perimeter tube joint. The length of the reinforcement member can be varied, and the reinforcement member itself weakened at some point along its length to vary the strength and allowed deflection under rear impact of the seat back. In the preferred embodiment the length of the reinforcement member can be varied, as well as features such as holes can be added to limit the strength, and increase the amount of energy that is absorbed at the joint. It also allows control of where the bending takes place. This allows common frames to be used across height and width variation, with their resulting differences in the amount of loads that they will absorb.

Additional effects, features and advantages will be apparent in the written description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a school bus.

FIG. 2 is a perspective view of a prior art school bus seat frame.

FIG. 3 is a perspective view of a modular school bus seat frame incorporating the present invention as installed in a vehicle.

FIG. 4 is an exploded view of the school bus seat frame illustrated in FIG. 4.

FIG. 5 is an exploded view of a joint between a riser and a seat back perimeter tube in which the reinforcement element of the present invention may be placed.

FIG. 6 is a perspective view of the reinforcement element of the invention.

FIG. 7 is an exploded view of a joint between a riser and a seat back perimeter tube illustrating an alternative location for positioning the reinforcement element during assembly.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and in particular to FIG. 1, a school bus 10 with which the present invention is advantageously used is illustrated. The seat frames of the present invention are installed in the interior 18 of the bus.

FIG. 2 illustrates a prior art seat frame 20 in which a closed, multi-piece full perimeter tube 26, which is closed on it self and forms an “L” outlining a base and seat back for the bus seat frame 20. A full perimeter tube 26 is supported by an aisle riser 22 and a wall riser 24. An internal frame 28 and a back seat support 30 are nestled within the closed perimeter tube 26. Excluding the risers 22, 24, virtually none of the components are reusable should seat specifications, such as width, or height of the seat back be changed. Internal frame 28 parallels portions of the perimeter tube 26, reinforcing the sides of the perimeter tube and adding a seat back bottom brace 34 and a cross member 32 to give the frame 20 rigidity.

Referring to FIG. 3, an assembled modular school bus seat frame 40 is illustrated supported in part from the floor 42 (shown in phantom) and along interior bus wall 44 (shown in phantom) from a chair rail 62 formed along the interior wall 44. Support from the floor 42 is provided by an aisle riser 46. Support from the wall 44 is provided by a wall riser 48. Aisle riser 46 and wall riser 48 differ from the aisle risers and floor risers known from the art illustrated in FIG. 2 in that they form more of the seat frame than is traditional in school bus applications. Both the aisle riser 46 and the wall riser 48 are modified to function as frame elements, in part by inclusion of necks 50 which provide bases of support for an open ended, partial perimeter tube 52 used to define the top and sides of a seat back portion of frame 40. The partial perimeter tube 52 is an upside down U shaped structural member mounted at opposite ends in necks 50 and defines the top and sides of the seat back. Suspended on and within the partial perimeter tube 52 is a seat back panel 54. Extending between and fitted into the aisle riser 46 and the wall riser 48 are front and back latitudinal supports 60 and 56. Supports 56 and 60 come in varying lengths to support seats of varying widths and fit into the risers to form joints. Risers 46 and 48 are molded elements with interior (i.e. facing) sides which are contoured to reinforce the riser.

FIG. 4 is an exploded view of the modular seat frame 40 which shows the major structural members of the seat frame. Necks 50 provide the location of the junction between the ends of the seat back perimeter tube 52 and the risers and are the locations where variable length reinforcement members 64 are located upon assembly of the seat frame 40. Necks 50 are C-channel sections extending upwardly from the upper rearward areas of aisle riser 46 and wall riser 48 and formed during the stamping process used to fabricate the risers. The open faces of the necks 50 face one another. Partial perimeter tube 52 fits by its opposite ends into the necks 50. The joints formed by joining the ends of the perimeter tube 52 to the necks 50 are reinforced by addition of reinforcement members 64 which fit into the neck 50 sandwiched between the tube 52 and the interior of the necks 50. Bolts 66 are inserted through the walls of the necks 50, reinforcement members 64 and the ends of perimeter tube 52 to complete the assembly.

Back panel 54 includes a partial perimeter lip 74 by which the panel is attached to tube 52. Risers 46, 48 include inner face contours 76 which position the ends of rear and front supports 56, 60. Risers 46, 48 have integral inwardly turned flanges 78 along their top and front edges. In addition, risers 46, 48 have a back edge flange 71, which are also inwardly turned. Flanges 71 and 78 provide surfaces against which opposite surfaces of the front and rear cross members 60, 56 may be placed to be secured by self pierce rivets (not shown), or other methods such as low temperature welding. Front cross member 60 is substantially formed in three panels, front panel 61, intermediate panel 63, and top panel 65 with panel 63 being intermediate to panels 61 and 65. The angle between panels 61 and 65 corresponds to the angle between the front and top edge sections of flange 78, allowing the cross member to be brought into contact with both portions of the flange concurrently. Panel 63 intersects both panels 61 and 65 obliquely along the respective interior side (i.e. the underside of the member relative to the risers) and positioned between the two panels functions as a cross brace between the flange 78 portions.

Rear cross member 56 incorporates two major sections, a top section 57 and a back section 59. The ends of top section 57 and back section are angled (essentially a right angle) to allow them flush mating of the sections to the under surface of the top portion of flange 78 and the forward surface of flange 71. Self pierce rivets (not shown), glue or welding are used to connect the member to the riser.

Aisle riser 46 includes legs which support the structure from the floor. A plate 68 is provided for securing fasteners between the riser 46 and a vehicle floor. Wall riser 48 includes an attachment lip 72 allowing securing of the wall riser to a wall support. Plate 68 and washer 70 are provided as part of the attachment process.

FIGS. 5 and 6 illustrated the variable length reinforcement member 64 and its use to construct a joint having controllable deformation and flexure characteristics. As already noted, reinforcement member 64 fits sandwiched between the perimeter tube 52 and necks 50 of risers 46 and 48 (only riser 46 is illustrated, though the member would typically be used identically with riser 48). The length of the reinforcement members 52 can be varied, and features such as holes 92 can be added to limit the members' strength, and increase the amount of energy that is absorbed at the joint. This further allows control of where bending takes place during a rear impact against the seat frame 40. Frames 40 can now be built which exhibit variation in height and width, with the differences in loads that they experience under conditions of impact handled by changes in the reinforcement member 64. The risers are typically an aisle riser 46 and a wall riser 48, though nothing would prevent use of the invention with a full width seat using opposed wall risers or a seat built on two aisle risers. Hence, in the claims the risers are referred to as first and second risers without differentiation regarding which type of riser is used.

In one embodiment, reinforcement member 64 is a three sided sleeve having opposed legs 90 and an open face, with examples positioned on the ends of perimeter tube 52 by welds 100. After introduction of the ends of perimeter tube into risers 50, the reinforcement member 64 is sandwiched between a lower riser stamping (46, 48) and the upper seat partial perimeter tube 52 with its open face aligned with the open side of the neck 50 in which it is situated. Thus the member 64 is located at the joint formed between the necks 50 and the ends of the partial perimeter tube 52. It overlaps the tube 52 of the upper frame, and extends above the joint for a distance that is varied according to the loading characteristics that are required. It can also be extended downward. Holes 92 are provided through which bolts 66 can be positioned and which strategically weaken the reinforcement member 64 at the desired locations. Members 64 are positioned to align holes 92 with holes 122 (see FIG. 7) through the ends of partial perimeter tube 52 and with holes 104 through the necks 50. In the embodiment illustrated in FIG. 5, member 64 is also attached to tube 52 using spot MIG (Metal in Inert Gas) welds. In effect, the seat frame can be tuned for strength characteristics between the lower seat and the seat back frame, and the degree of allowed deformation controlled, with the use of only two reinforcement members.

FIGS. 5 and 6 illustrated the variable length reinforcement member 64 and its use to construct a joint having controllable deformation and flexure characteristics. As already noted, reinforcement member 64 fits sandwiched between the perimeter tube 52 and necks 50 of risers 46 and 48 (only riser 46 is illustrated, though the member would typically be used identically with riser 48). The length of the reinforcement members 52 can be varied, and features such as holes 92 can be added to limit the members' strength, and increase the amount of energy that is absorbed at the joint. This further allows control of where bending takes place during a rear impact against the seat frame 40. Frames 40 can now be built which exhibit variation in height and width, with the differences in loads that they experience under conditions of impact handled by changes in the reinforcement member 64. The risers are typically an aisle riser 46 and a wall riser 48, though nothing would prevent use of the invention with a full width seat using opposed wall risers or a seat built on two aisle risers. Hence, in the claims the risers are referred to as first and second risers without differentiation regarding which type of riser is used.

In its preferred embodiment, reinforcement member 64 MIG welded to the inside of neck 50 with its open side coinciding with the open side of the neck. Both neck 50 and reinforcement member 64 are three sided sleeves and an open face. Upon assembly, the reinforcement member becomes sandwiched between the lower riser stamping (46, 48) and the upper seat partial perimeter tube 52 as in the prior embodiment. Again the member 64 is located at the joint formed between the necks 50 and the ends of the partial perimeter tube 52. It overlaps the tube 52 of the upper frame, and extends above the joint for a distance that is varied according to the loading characteristics that are required. It can also be extended downward. Holes 92 of the reinforcement member 52 are provided through which bolts 66 can be positioned and which strategically weaken the reinforcement member 64 at the desired locations. Members 64 are positioned to align holes 92 with holes 122 through the partial perimeter tube 52 and with holes 104 through the necks 50. Member 64 is also attached to the inside of neck 50 using spot MIG (Metal in Inert Gas) welds.

While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention. 

1. A modular seat frame comprising: first and second risers; a partial perimeter tube for a seat back frame supported from the first and second risers at joints formed between opposed ends of the perimeter frame and open necks in the first and second risers; and reinforcement members located in the joint overlapping portions of the partial perimeter tube and the necks of the first and second risers.
 2. A modular seat frame as claimed in claim 1, further comprising: the reinforcement members being open channel members fitting outside of the partial perimeter tube and inside of the necks and being shaped to conform to the section shapes of the partial perimeter tube and neck sandwiched between the two.
 3. A modular seat frame as claimed in claim 2, further comprising: the reinforcement members having lengths chosen to control strength of the joints and to control deformation of the seat back frame upon rear impact into the seat back frame.
 4. A modular seat frame as claimed in claim 2, further comprising: the reinforcement members having holes located to control strength of the joints and to control deformation of the seat back frame upon rear impact into the seat back frame.
 5. A modular seat frame as claimed in claim 3, further comprising: installation on a school bus.
 6. A modular seat frame as claimed in claim 4, further comprising: installation on a school bus.
 7. A modular seat frame as claimed in claim 2, further comprising: the reinforcement members being welded to the ends of the perimeter tubes.
 8. A modular seat frame as claimed in claim 2, further comprising: the reinforcement members being welded to the inside surfaces of the open necks. 